'Floatavoltaics' Generate Electricity and Solve Water Problems

Some of the most interesting technological discoveries have been accidental, including one that began several years ago at the Far Niente winery in Napa Valley, Calif. SPG Solar, a major solar integration company, was asked to design a solar-power system to help provide electricity for the winery.
Far Niente owned some of the world’s most valuable wine-producing land and wanted to use as little of it as possible for a solar array. SPG engineers proposed a novel, first-of-its-kind solution: float 994 photovoltaic panels on pontoons, cover a one-acre spring-fed pond, and generate 207 kW of power.

Then things began to happen that no one expected. Algae growth began to disappear and no longer had to be chemically controlled. Water quality and marine life improved. Electricity production rose higher than estimated. Most surprisingly, the pond produced more water for irrigation than ever before. And in California agriculture today, water is liquid gold.

Shortly thereafter, university scientists began studying the phenomena. They found the water the panels float on acts as a natural heat-sink, keeping the panels cooler than if mounted on a rooftop or on land-mounted racks. That accounted for the increased power output.

It turned out that the evaporation rate in sunny Northern California was huge—7 to 8 vertical feet of evaporation every year. The panels blocked about 80 percent of the evaporation on the surface by shading, blocking wind from blowing on the surface and by physically capping the surface, so it’s not exposed to air.

Besides increased power production and water conservation, the most promising discovery was that the panels keep chlorine out of the water. It is not just an expensive chemical but creates bromates and other carcinogenic chemicals that endanger public water supplies. Environmental regulations are tightening on how much chlorine can be added to drinking water, and water districts may be mandated to build multimillion-dollar third-stage treatment facilities. That is why large water districts like Los Angeles are keenly interested in “floatavoltaics.” California water districts own thousands of water-retention facilities where public recreation is banned, which are ideal sites to install floating solar panels.

Floating solar panels on small areas of these bodies of water could help mitigate the chlorine problem, produce renewable energy and conserve millions of acre-feet of water to help alleviate water shortages. This development is drawing water delegations from around the world to evaluate the technology. Meanwhile, SPG is busy building second-generation floatavoltaics.